Bar bending schedule (BBS) of a sunshade. (Type-2) / Calculating the cutting length & weight of reinforcement in a chajja. ~ PARAM VISIONS

Type-1 👈 Back

Let us make BBS of the Chajja or RCC sunshade as shown below.

Given data:

Length of chajja = 1000mm.

Width of chajja = 600mm.

Chajja thickness (front) = 75mm.

Lintel beam width = 230mm.

Lintel beam depth = 400mm.

Main bar ( gun bar) = 10∅ @ 150c/c.

Distribution bar = 8∅ @ 150 c/c.

Clear cover of chajja =20mm.

Lintel beam cover = 25mm.

Calculation:

A. Cutting length:

1. Cutting length of the main bar (gun bar):

Cutting length of the gun bar

= [ (ab + bc + cd + de + ef + fg +gh + hi) - (6nos. × 90° bend. + 1no. × 135° bend.)]

Where,

ab = [chajja thickness - (2nos. × cover) ]

= [75mm. - ( 2nos. × 20mm.) ]

= 35mm.

bc = [ (chajja width - chajja cover) + (beam width - beam cover)]

= [ (600mm. - 20mm.) + (230mm. - 25mm.)]

= [ 580mm. + 205mm.]

= 785mm.

cd = [ chajja thickness - chajja cover - beam cover]

= [ 75mm. -20mm. - 25mm.]

= 30mm.

de = [ beam width - (2nos.× cover) ]

= [ 230mm. - (2nos.× 25mm.) ]

= 180mm.

ef = [ beam depth - (2nos.× cover) ]

= [ 400mm. - (2nos.× 25mm.) ]

= 350mm.

fg = de = 180mm.

gh = ef = 350mm.

hi = hook length

= 12d = [12 × 10mm.]

= 120mm.

Now, the cutting length of the gun bar

= [ (35mm. + 785mm. + 30mm. + 180mm. +350mm. + 180mm. + 350mm. + 120mm.) - (6nos. × 2 × 10mm. + 1no. ×3 × 10mm.)]

= [ 2030mm.- 150mm.]

= 1880mm.

= 1.88m.

2. Cutting length of distribution bar

= [ chajja length - (2nos.× sunshade cover)]

= [ 1000mm. - ( 2nos. × 20mm.)]

= 960mm.

= 0.96m.

B. No. of bars:

1. No. of main bars/gun bars.

= [{chajja length - (2nos. × cover)} ÷ c/c distance ] +1

= [{1000mm. - (2nos. × 20mm.)} ÷ 150mm. ] +1

= [ {960mm.} ÷ 150mm. ] +1

= 6.4 +1

= 7.4

By rounding off = 8 nos.

2. No. of distribution bars

= [{chajja width - cover - main bar dia} ÷ c/c distance ] +1

= [{600mm. - 20mm. - 10mm} ÷ 150mm. ] +1

= [ {570mm.} ÷ 150mm. ] +1

= 3.8 +1

= 4.8

By rounding off = 5 nos.

If you want to know, how to prepare BBS of lintel beam, Go through the article👇

💁 ° How to calculate the cutting length & make BBS of the Lintel bar.

Now, let us prepare a BBS table for the Chajja or sunshade.

Sl. No.	Type of Bar	Dia. in mm.	Nos.	Length in m.	Total length in m.	Weight in Kg/m.	Total bar wt. in kg.
1.	Main bar.	10	8	1.88	15.04	0.612	9.20
2.	Distribution bar.	8	5	0.96	4.80	0.395	1.90
3.	Total weight of steel bars =						11.10
4.	Add 3% wastage =						0.33
5.	The grand total wt. of rebar's in chajja =						11.43